Phase I recruitment, an anonymous online survey, took place between April 30 and May 13, 2019. The primary AIM of Phase I was to characterize the levels and types of fatigue experienced by RNs, and to examine the physiologic, psychologic and situational factors contributing to fatigue and its subtypes in RNs. The secondary AIM was to examine the relationship between fatigue with cognitive performance, life satisfaction, and the ability to participate in social roles/activities in RNs. A series of three recruiting emails were sent to all 1181 RNs credentialed through the NIH Clinical Center. This survey asked basic demographic and general workplace questions on employment status, job type (e.g., staff nurse, administrative, research), and hours worked, etc. It also collected self-reported information on levels and types of fatigue, and potential correlates of fatigue including situational/workplace factors (burnout, work demands, work supports, and inter shift recovery), physiologic factors (BMI, physical health, sleep disturbance), psychological factors (depression, anxiety, coping style, and self-efficacy), and performance measures (cognitive function, social role ability, life satisfaction). Three hundred thirteen (26.5%) RNs accessed the link and completed the survey. Phase I of this study is currently in the data analysis phase.